Abstract:

In alignment with the European Union’s 2050 carbon neutrality targets, the automotive industry is intensifying efforts to adopt lightweight materials that ensure structural integrity without compromising safety. Press-hardened steels (PHS), offering a combination of ultra-high strength and formability, are at the forefront of these developments. Standard PHS grades rely on Ti-B microalloying; however, further alloying with Nb and V has been proposed to enhance hydrogen embrittlement resistance via microstructural refinement and hydrogen trapping. This study investigates hydrogen transport and mechanical degradation in a Ti-Nb-V microalloyed PHS compared to a conventional Ti-only 22MnB5 grade. Electrochemical permeation, thermal desorption, and mechanical testing were employed to characterize hydrogen diffusivity, solubility, and trapping mechanisms. The Ti-Nb-V variant demonstrated lower hydrogen diffusivity, higher solubility, and improved resistance to delayed fracture, attributable to the presence of fine NbTiV precipitates.

Abstract: Complementing the steady state modeling of an ideal solar evaporation pond, the present study is concerned with the dynamic modeling of the ideal solar evaporation pond for Li extraction from brines. The approach conceptualizes the pond as a sequence of discrete particles of brine of suitable size with continuous feeding and discharging considering water evaporation events over time. The discrete dynamic model produces a dynamic concentration profile over time, which converges to a steady-state concentration profile equal to that predicted by the ideal solar evaporation law. This discrete dynamic particle model allows for variations in feed flow rate, evaporation rate per unit area, feed concentration, and pond area. This approach allows the visualization of concentration perturbations propagating at a finite speed through the system exhibiting a hyperbolic nature. The model was validated using average lithium, boron, and magnesium concentrations obtained from an industrial pond system at the Salar de Atacama, Chile, in the year 2023. Therefore, this discrete dynamic model constitutes a versatile tool for analyzing and optimizing the performance of solar evaporation pond systems under variable operating conditions.

Abstract: The pitting corrosion resistance and the tribological behaviour of a ferritic stainless steel with high Mo content (AISI 436) and a commonly employed austenitic stainless steel (AISI 304) are compared. Special attention was paid to the role of Mo in improving corrosion resistance of ferritic stainless steels. Since the surface condition is an important parameter related to the onset of pitting corrosion in the presence of chlorides, three different surface finishes were tested for both steels. Two commercial finishing grades and laboratory polishing down to 1 µm were compared. Moreover, the influence of surface condition on the tribological properties for both steels was also evaluated. The study demonstrates that surface finishing plays a decisive role in both the electrochemical and mechanical response of stainless steels. A comprehensive microstructural and tribological analysis reveals not only how commercial finishing treatments modify passive film behaviour, but also how they affect friction stability and wear mechanisms. Special emphasis is placed on the synergistic effect between molybdenum content, passive film integrity and manufacturing processes. The obtained results provide valuable insight for industrial applications where durability against chloride exposure and abrasion is critical.

Abstract: Grey cast iron brake discs are widely used in automotive applications due to their excel-lent thermal and mechanical properties. However, stricter environmental regulations such as Euro 7 demand improved surface durability to reduce particulate emissions and corro-sion-related failures. This study evaluates multilayer coatings fabricated by Laser Metal Deposition (LMD) as a potential solution. Two multi-layer systems were investigated: 316L+(316L+WC) and 316L+(430L+TiC), which were primarily reinforced with ceramic additives to increase wear resistance, with their influence on corrosion being critically evaluated. Electrochemical tests in 5 wt.% NaCl solution (DIN 17475) revealed that the 316L+(316L+WC) coating exhibited the lowest corrosion current density and most stable passive behavior, consistent with the inherent passivation of the austenitic 316L matrix. In contrast, the 316L+(430L+TiC) system showed localized corrosion associated with mi-cro-galvanic interactions, despite the chemical stability of TiC particles. Post-corrosion SEM and EDS confirmed chromium depletion and chloride accumulation at corroded sites, while WC particles exhibited partial dissolution. These findings highlight that ce-ramic reinforcements do not inherently improve corrosion resistance and may introduce localized degradation mechanisms. Nevertheless, LMD-fabricated multilayer coatings demonstrate potential for extending brake disc service life, provided that matrix–reinforcement interactions are carefully optimized.

Abstract: Titanium alloys are widely employed for biomedical implants due to their favourable combination of strength, corrosion resistance, and biocompatibility. A drawback, however, is the lack of intrinsic antibacterial functionality. In this study, Ti 6Al 7Nb was modified with varying copper (Cu) contents (1 wt.% – 9 wt.%) via in situ alloying during metal based laser powder bed fusion (PBF-LB/M) to investigate the processing behaviour, microstructural evolution, and mechanical properties. Powder mixtures were processed under systematically varied laser parameters, with densification, surface quality, and microstructure assessed by microscopy and X-ray diffraction, while hardness and tensile properties were characterised through mechanical testing. The results demonstrate that dense samples (> 99.9 %) can be achieved for all investigated copper amounts, although the homogeneity is strongly dependent on the process parameters. An increasing copper content promotes β-phase stabilisation, Ti₂Cu precipitation, and significant grain refinement with a transition from columnar to equiaxed structures. Hardness and yield strength increase nearly linearly with increasing copper content, while the ductility decreases sharply at ≥ 5 wt.% Cu due to intermetallic formation, hot cracking, and brittle fracture mechanisms. These findings highlight both the potential and the limitations of copper additions in Ti 6Al 7Nb processed by PBF LB/M. Overall, moderate additions of 1 wt.% – 3 wt.% Cu appear most promising, offering improved mechanical performance while preserving sufficient ductility and manufacturability for biomedical applications.

Abstract: Enhancing the local mechanical response of low-carbon cast steels remains essential for improving their performance in wear-intensive environments. In this work, a low-carbon cast steel was locally modified through the in situ formation of TiC particles via melt reaction with pressed Ti–Al–C powders. Advanced microstructural characterization (SEM/EDS, EBSD, and TEM) revealed a heterogeneous TiC-reinforced composite microstructure containing ~36 vol.% TiC with particle sizes between 0.73 and 3.88 μm. The reinforced region exhibited a substantial increase in hardness, from 160 ± 5 HV30 in the base steel to 407 ± 78 HV30, resulting from the synergistic contribution of TiC particles, fine κ-carbides, and a martensitic matrix. Nanoindentation revealed a strong mechanical contrast between phases, with TiC achieving 25.70 ± 7.76 GPa compared to 4.68 ± 1.09 GPa for the base metal matrix. Micro-abrasion tests showed a 24% reduction in wear rate, accompanied by shallower grooves and reduced plastic deformation. These findings demonstrate that in situ TiC formation, combined with κ-carbide precipitation, provides an effective strategy for improving local hardness and abrasive wear resistance in low-carbon cast steels. The results highlight the potential of in situ composite formation as an effective microstructural engineering strategy for next-generation wear-resistant cast steels.

Abstract: This study investigates the feasibility of efficiently recovering lead and silver from a lead cake by applying a combined process of chlorination roasting followed by acid leaching. The lead cake is obtained after the sulfuric acid leaching of zinc ferrite residues generated during the hydrometallurgical treatment of zinc calcine. The influence of roasting temperature, the mass ratio between lead cake and NaCl, and the roasting duration on metal extraction was systematically investigated to determine optimal process conditions. The most efficient parameters were identified as roasting at 550 °C for 1.5 hours with a lead cake to NaCl ratio of 1:3, followed by leaching the roasted product in 1 M HCl. Under these conditions, the remaining Pb and Ag contents in the final solid residue were reduced to 0.90 % and 0.0027 %, respectively, indicating nearly complete chlorination and subsequent dissolution of both metals. A comparative evaluation showed that the combined chlorination roasting–leaching approach resulted in higher recovery rates (Pb 98.67 %, Ag 98.09 %) and a smaller final residue mass than direct chloride leaching (Pb 96.79 %, Ag 84.55 %). Therefore, the proposed method is demonstrated to be more effective and environmentally advantageous for recovering valuable metals from industrial waste materials.

Abstract: To address the technical challenges in the resource utilization of hot metal containing high levels of vanadium (V: 2–5%) and chromium (Cr: 1–5%), this paper proposes a novel method based on pyrometallurgical selective oxidation for the simultaneous extraction of vanadium and retention of chromium. Through thermodynamic analysis and high-temperature smelting experiments, the competitive oxidation behaviors of carbon, vanadium, and chromium were revealed, and the synergistic control mechanism of temperature and oxygen partial pressure was clarified. The results indicate that within the temperature range of 1693–1753 K, vanadium preferentially oxidizes over carbon and chromium, while carbon effectively suppresses chromium oxidation. By optimizing the ω(FeO) (10.0–15.7%), achieving a vanadium oxidation efficiency (ηV) of 72.5–82.2% and maintaining the chromium retention efficiency (1–ηCr) exceeding 57.1%. Compared to traditional methods—which rely on high-oxygen blowing (oxygen supply: 43–195 kg/tFe), multi-stage roasting, and hydrometallurgical refining—this approach eliminates roasting and hydrometallurgical steps, shortens the process chain, reduces oxygen consumption (> 80 kg/tFe), and lowers environmental risks (Cr oxidation reduced > 40%). The study establishes a theoretical framework for sustainable V/Cr separation, enhancing resource efficiency and minimizing pollution.

Abstract: The Mg-Y-Zn alloy system is well known for its outstanding combination of high strength and ductility, even at relatively low concentrations of alloying elements. This exceptional performance is primarily at-tributed to its characteristic microstructure, which features Long-Period Stacking Ordered (LPSO) phases and the distinctive Mille-Feuille Structure (MFS). Kink-induced strengthening, developed during thermomechanical processing, has emerged as a promising strategy to simultaneously enhance strength and ductility. In this study, the beneficial effect of pre-deformation aimed at introducing additional kinks into the microstructure prior to extrusion is demonstrated. The subsequent extrusion process promotes dynamic recrystallization (DRX), generating fine DRX grains while preserving kink structures in the non-DRX regions. As a result, the yield strength is enhanced by approximately 80 MPa, accompanied by a slight improvement in ductility.

Abstract: This study develops a sustainable welding approach by incorporating 35–50% blast furnace slag (BFS), a byproduct of the steel industry, into rutile-type electrode coatings. Electrodes were fabricated by dry mixing BFS with fluxes, adding potassium silicate binder to form a paste, pressing at 150 bar onto a 3.25 mm core wire, and heat treatment at 150°C for two hours. Weld quality and performance were evaluated through visual inspections, microstructure and XRD analyses, hardness, tensile, and impact tests. Visual inspections confirmed weld quality comparable to commercial standards, with stable arc and minimal spatter. Microstructure analysis revealed a fer-rite-dominated weld metal with TiO₂ and FeTiO₃ phases in the slag layer, enhancing strength and toughness. Electrodes with 35–40% BFS achieved yield strength of 477–482 MPa, tensile strength of 570–573 MPa, and impact energy of 58–59 J at 0°C, complying with ISO 2560:2020. BFS integration reduced CO₂ emissions by 0.28–0.4 kg per kg of coating and diverted 200–600 kg of slag per ton of steel from landfills. Coating and raw material costs decreased by 33–48% and 15–25%, respectively, aligning with the EU Green Deal’s circular economy goals and enhancing weld quality and sustainability.

Abstract: This study explores the application of lattice structures as internal support architectures in the fabrication of Inconel 718 components via Laser Powder Bed Fusion (L-PBF), building upon previous research on beam-based FCCZ supports. Two representative lattice typologies were investigated: the node and beam-based FCCZ structure and the triply periodic minimal surface (TPMS) Schoen Gyroid cell. The aim was to assess how the transition from a discrete beam-node architecture to a continuous surface topology influences manufacturability, thermal stability, and mechanical performance. Finite Element Method (FEM) simulations in Ansys accurately predicted distortions and residual stresses during the L-PBF process, showing strong agreement with stereomicroscope measurements. After fabrication, the samples underwent solution treatment and double aging according to AMS 2774 and AMS 5662 standards. Microstructural analysis using optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) revealed that heat treatment partially homogenized the microstructure but did not achieve complete recrystallization, leaving localized dendritic regions and undissolved Laves phases, particularly near the lattice. The precipitation of γ′ and δ phases enhanced hardness and mechanical uniformity, as confirmed by Vickers microhardness testing. Overall, the Gyroid topology demonstrated superior manufacturability and thermal stability, exhibiting reduced defects and deformation compared to the FCCZ structure. These findings confirm its potential as an efficient and reliable self-supporting architecture for L-PBF Inconel 718 components intended for high-performance and thermally demanding applications.

Abstract: The present study systematically investigates the effect of homogenization treatment on the microstructural evolution, recrystallization behavior, and mechanical response of a hot-rolled Mg-3Al-1Zn-1Ca alloy. Detailed microstructural characterization revealed that Al2Ca precipitates were uniformly distributed along grain boundaries in the as-received (AR) condition, where they contributed to significant pinning of boundary migration. Homogenization treatment (350 °C, furnace cooling) resulted in non-uniform grain coarsening, driven by the interplay of precipitate pinning and differential stored strain energy, while also facilitating particle-stimulated nucleation (PSN) and recrystallization. Electron backscatter diffraction (EBSD) analysis confirmed a substantial increase in the fraction of high-angle grain boundaries and recrystallized grains in the heat-treated (HT) state, with kernel average misorientation (KAM) and grain orientation spread (GOS) analyses indicating pronounced recovery of lattice distortions. Mechanical testing demonstrated a significant decrease in yield strength (263 MPa to 187.4 MPa) and hardness (65.7 to 54.1 HV) due to dislocation annihilation and stress relaxation, while ultimate tensile strength remained nearly unchanged (~338 MPa) and ductility improved markedly (12.6% to 16.4%). These findings highlight the dual role of Al2Ca precipitates in promoting recrystallization through PSN while simultaneously restricting excessive grain growth through Zener pinning.

Abstract:

Ti-6Al-4V is valued for its strength-to-weight ratio in engineering applications. Cryo-rolling at sub-zero temperatures enhances strength and hardness through grain refinement and dislocation build-up. Present study investigates the role of cryo-rolling on the microstructural characteristics and mechanical properties of the alloy, which undergoes various degrees of deformation followed by heating at 900 °C for selected samples. Microstructural analysis reveals grain elongation, sub-grain formation, deformation bands, and dislocation densification with increasing thickness reduction. Twinning dominates deformation at low strain, while dislocation slips take over at high strain because of the decrease in grain size, which makes the formation of new twins progressively more challenging. No metastable phase appears during cryo-rolling or heat treatment, as confirmed by X-ray diffraction. Cryo-rolled samples exhibit about 45% and 28% reduction in grain size and crystallite size, and 152% intensification in dislocation density. This leads to rises of 23%, 19%, and 8% in yield strength, tensile strength, and hardness, respectively, while ductility remains nearly constant across all cryo-rolled conditions. Cryo-rolling inhibits dynamic recovery and recrystallisation, so strengthening mainly results from grain refinement and dislocation accumulation. These findings suggest that cryo-rolling can improve the strength and hardness of Ti-6Al-4V, while maintaining ductility and providing new processing insights.

Abstract: Micro-arc oxidation (MAO) technology demonstrates remarkable advantages in fabricating ceramic coatings on lightweight alloys. For aluminum alloys, MAO rapidly forms dense, pore-free ceramic layers within minutes, significantly enhancing corrosion and wear resistance at low processing costs. In magnesium alloys, optimized electrolyte compositions and process parameters enable composite coatings with combined high hardness and self-lubrication properties, while post-treatments like laser melting or corrosion inhibitors extend salt spray corrosion resistance. Titanium alloys benefit from MAO coatings with exceptional interfacial bonding strength and mechanical performance, making them ideal for biomedical implants and aerospace components. Notably, dense ceramic oxide films grown in-situ via MAO on high-entropy alloys (HEAs) triple surface hardness and enhance wear/corrosion resistance. However, MAO applications on steel require pre-treatments like aluminizing, thermal spraying, or ion plating. Current challenges include coating uniformity control, efficiency for complex geometries, and long-term stability. Future research focuses on multifunctional coatings (self-healing, antibacterial) and eco-friendly electrolyte systems to expand engineering applications.

Abstract: It is crucial for the efficiency and the productivity of operations that the viscous flow behavior of the CaO-SiO₂-MgO-Al₂O₃-B₂O₃ blast furnace slag systems. In this paper, the effects of CaO/SiO₂ and MgO/Al₂O₃ on the viscosity, the break point temperature (TBr) and activation energy (Eη) of low boron-bearing high alumina slag were considered in detail. Meanwhile, the effect mechanisms of CaO/SiO₂ and MgO/Al₂O₃ on slag viscous behavior were expounded using the X-Ray Diffraction (XRD), Fourier transformation infrared spectroscopy (FTIR) and the Factsage. The results show that, with the increasing of CaO/SiO₂ from 1.10 to 1.30，the viscosity at 1773 K decrease from 0.316 Pa·s to 0.227 Pa·s ,the TBr and Eη increase from 1534 K and 117.01 kJ·mol-1 to 1583 K and 182.86 kJ·mol-1 respectively. With the increasing of MgO/Al₂O₃ from 0.40 to 0.65，the viscosity at 1773 K and the TBr decrease from 0.290 Pa·s and 1567 K to 0.208 Pa·s and 1542 K respectively. The deterioration of slag behaviors is due to the increase of polymerization degree of complex viscous units in the slag. Ultimately, when CaO/SiO₂ at 1.25 and MgO/Al₂O₃ at 0.55, the viscous behaviors of slag are better.

Abstract: The thermomechanical process to obtain high alloy high strength steels is based on the control of variables such as temperature, deformation and strain rate to promote hardening mechanisms that directly influence the strength and toughness of the steel. Experimentally, it was determined for an API type steel, that the temperature of potential precipitation during the hot deformation process will be in a range of temperature from 1150°C to 1000°C. Precipitation will occur instantaneously due to temperature, deformation and strain rate (0.1 and 0.2 deformation and 0.5s-1 and 1s-1 strain rate) effect. The incorporation of microalloying elements as Nb in a percentage of < 0.050 significantly influences precipitation hardening preferentially located at austenitic grain boundaries. It was determined that precipitates of between 3 to 5 nanometers in size, distinguished as NbC will be obtained. It was found that the precipitation kinetics for the steel is affected by a single step deformation applied, by the formation of precipitate colonies at 0.1 deformation and strain rate 1s-1, which does not allow the dispersion of precipitates generating a planar interface in the microstructure of the steel. Finally, the preferentially localized precipitation mechanism of the almost continuous type by the grain boundaries was evidenced. This mechanism is crucial for controlling austenitic grain size during deformation, which leads to a final, homogenized microstructure.

Abstract: Solidification cracking and liquation cracking have been reported frequently in additive manufacturing (AM) as well as welding. In the vast majority of weldability tests, a single-pass, single-layer weld is tested though multiple-pass, multiple-layer welding is common in welding practice. In AM, evaluating the cracking susceptibility based on the total number or length of cracks per unit volume requires repeated cutting and polishing of a built object, and the cracks are often too small to open easily for fracture-surface examination. The present study identified an existing weldability test and modified it to serve as a cracking susceptibility test for AM. A single-pass, single-layer deposit of metal powder was made along a slender specimen that was pulled like in tensile testing but with acceleration. Cracks were visible on the deposit surface and opened easily for examination. The critical pulling speed, i.e., the minimum pulling speed required to cause cracking, was determined as an index for the cracking susceptibility. The lower the critical pulling speed is, the higher the cracking susceptibility. 6061 Al and 7075 Al alloys were selected for testing in view of their high susceptibility to solidification cracking and liquation cracking in welding, respectively.

Abstract: New proposals include the precipitation of new phases and intermetallics in light alloys occur on bifilms rather than on grain boundaries (confusion is understandable because, commonly, it seems that as many as 50 per cent of grain boundaries contain bifilms). The formation and growth on bifilms result from the saving of plastic work to accommodate the volume and shape change of the new phase, which can be orders of magnitude higher than the saving of interfacial energy on grain boundaries. The bifilm, if previously closed, is forced to open by this process, called ‘Precipitation Cleavage’. The term ‘cleavage’ refers to the cleaving open of the bifilm, dispers- ing the volume change elastically over a relatively extensive area. This is the mechanism explain- ing the sensitisation heat treatments for (i) embrittlement, (ii) invasive corrosion as in stress corro- sion cracking, and (iii) invasion of hydrogen into opened bifilms as ‘sinks’, leading to surface blis- tering and hydrogen embrittlement of the matrix. Direct visual evidence is provided by (i) surface blisters during hydrogen charging, and (ii) fracture surfaces displaying quasi cleavage facets, and fisheyes observed in steels and more recently also in light alloys.

Abstract: The (AlFeCoNi)C high-entropy alloy carbide films (HECFs) with tunable carbon contents were fabricated by magnetron sputtering to investigate the carbon-driven structural evolution and its coupling effects on mechanical and chemical properties. With increasing carbon incorporation (0-47.6 at.%), the HECFs formed a composite structure of amorphous phase and BCC nanocrystalline phase, as evidenced by XRD and TEM. Atom probe tomography (APT) reveals Al segregation in the film. Remarkably, the wear rate decreases exponentially from 5.3×10⁻⁵ to 1.3×10⁻5 mm³/N·m, attributed to the amorphous carbon phase acting as solid lubricant. Simultaneously, the corrosion current density reduces by two orders of magnitude (7.2×10⁻⁸ A/cm² in 3.5% NaCl), benefiting from the amorphous network inhibiting ion diffusion pathways. This work establishes a carbon-content-property correlation paradigm for designing multifunctional HEA films in extreme environments.

Abstract: We propose a new principle of adaptive Severe Plastic Deformation (SPD) processes, in which contact pressure stems from the reaction of the tool, rather than a force exerted on the workpiece externally. The reaction owes to special tool design utilizing a wedge effect. This approach ensures self-regulation of the deformation mode without the need for complex bidirectional loading systems. In addition, the equipment for adaptive processing can operate at loads which are substantially lower than those required for conventional SPD processing. Adaptability is analyzed by way of example for the High Pressure Sliding (HPS) process, for which theoretical justification, numerical calculations by the finite element method, and experimental verification are provided. It was established that, thanks to the self-regulation mechanism, the pressure is maintained automatically at the level necessary for plastic deformation of the workpiece. Experiments on copper samples showed the formation of an ultra-fine-grained structure. The results obtained demonstrate the efficacy of the adaptive HPS and open prospects for its application in the processing of thin-walled metal products.